High-Speed GMAW and Laser GMAW Hybrid Welding of Steel Sheet

High-Speed GMAW and Laser GMAW Hybrid Welding of Steel Sheet Ian D. Harris, Ph.D.

Technology Leader, Arc Welding

EWI, Columbus, Ohio   Abstract

A fundamental problem and limitation to the use of higher travel speeds in GMAW is the phenomenon of weld bead humping, a weld profile defect with a wavelike profile to the weld bead that has peaks and troughs in the longitudinal direction.

The initial hypothesis was that the humping defect can be suppressed and continuous beads deposited at much higher speeds by using a laser beam welding (LBW) in the conduction mode at the weld toes to improve bead wetting thus minimizing bead convexity which, at toe angles below 90 degrees, tends to promote the formation of the humping defect.  This was investigated by a research program intended to develop an understanding of the cause of the humping defect, and included extensive use of high-speed video (HSV) to determine the root cause, from which the mechanisms were determined.   The main elements of the research were as follows;

 

• GMAW-P parameters for welding with 0T and 1T gaps
• High-speed GMAW-P with 0T gap
• Hybrid LBW/GMAW-P using CO₂ and Nd:YAG lasers
• HSV of GMAW-P and bead humping

The hypothesis was demonstrated and, for the welding techniques investigated, the following maximum TS can be stated:

 

1. Conventional GMAW-P – typical maximum TS of 1 m/min
2. High speed GMAW-P – typical maximum TS of 2 m/min
3. Hybrid conduction mode laser/GMAW-P – typical maximum TS of 3.5-4 m/min

 

1. HSV of GMAW-P showed the humping defect to be caused by a repetitive arc instability that causes the forming hump to move first forward and then backward at the moment of the instability.

The major benefit of this work is the increased understanding of high speed welding and the potential to significantly increase welding productivity.